1. Field of the Invention
The invention resides in the field of heat exchangers, and more particularly, in the field of attachment or securement of heat exchange surfaces, particularly fins to tubular members. The invention is particularly adapted for utilization in solar heat collecting systems.
2. Description of the Prior Art
Heat exchangers comprising finned, tubular members are well known. With respect to the attachment of heat exchange surfaces or fins to tubular members, various types of construction are known. Fins may be fabricated integrally with the tubes. They may be attached by welding or soldering, that is, securing inner edges of the fins to the tubes. The fins may have flanges which are welded to the tubes. The tubes may have flanges which are brazed together forming a heat exchanger. Helical fin material may be wrapped around the tube. A typical construction involves providing holes in fin or heat exchange surfaces, the tubes being inserted through the holes and the tube diameters expanded by manual or hydraulic pressure to engage the peripheral edges of the holes.
Quite often, a thermoconductive paste is used to improve (decrease) the contact resistance. This paste is made of a highly conductive material and tends to fill up all the voids and crevices which would normally be filled with air, which is a poor conductor. However, thermoconductive paste is relatively expensive.
The prior art methods described rely on welding or increasing the diameter of the tube to obtain an interference fit.
Prior art patents are: U.S. Pat. Nos. 1,982,075; 3,280,530; and 3,379,241.
The herein invention realizes finned tube construction which is entirely unique, as is the method or technique of fabricating as described hereinafter.